1. Field of the Invention
The present invention relates to a process for the production of 3,5,6-trihydroxyhexanoic acid derivatives.
The 3,5,6-trihydroxyhexanoic acid derivatives are useful as intermediates in the synthesis of a series of HMG-CoA (Hydroxy methyl glutaryl-CoA) reductase inhibitors which are attractive as anti-hyperlipemia agents.
2. Description of the Related Art
To prepare the 3,5,6-trihydroxyhexanoic acid derivatives, the following processes are known:
(A) A process using L-malic acid as a starting material (cf. Japanese Patent Kokai Publication No. 22056/1988): ##STR4##
(B) A process using 1,3,5-trihydroxybenzene (Phloroglucinol) as a starting material (cf. Tetrahedron Letters, 23, 2435 (1984) and U.S. Pat. No. 4,571,428): ##STR5##
(C) A process using an allyl alcohol derivative as a starting material (cf. Tetrahedron Letters, 25, 3391 (1984)): ##STR6##
Among the above conventional processes, the process (A) has an advantage that the product can be obtained in an optically active form. However, the process (A) requires a multistage reaction and relatively expensive reagents such as carbonyl diimidazole.
In the process (B), although the reaction time is not long, the product is obtained in the form of racemate. The useful compound as HMG-CoARI intermediate should have a (3R, 5S) configuration.
The third process (C) gives the optically active product. However, there is no optical selectivity in the reaction of an aldehyde and ethyl bromoacetate. Therefore, this process is not industrially attractive.